This invention lies in the field of gas flow measurement. More particularly, it lies in the field of electronic integration of gas flow rate to provide total flow during a selected period. Still more particularly, it involves a mechanism for manually transcribing the traces of pressure and differential pressure on circular flow charts, and by proper encoding of the rotation of the chart table and of the two angular motions of the two pen arms, provides a running integral of the flow.
In many industries, such as the chemical and petroleum industries, large volumes of gas flow must be metered for various reasons, but mainly because of the fact that gas is valuable, and is bought and sold, and gas flow must be determined precisely so that the proper payments can be determined and made.
For over 50 years the conventional method of measuring gas flow was by means of a circular chart flow recorder, which determined the gauge pressure of the gas and the differential pressure across an orifice plate inserted into the flow line. Dependent on the size and shape of the orifice the flow rate is determined by the product of a constant C which is the calibration constant of the orifice, times the magnitude of square root of absolute pressure times the square root of differential pressure.
In the prior art there have been many different types of mechanical integrators, using wheel and disc type multipliers and various types of cams for determining square roots, etc.
Each of these mechanical systems utilizes the measurement of angle of two pen arms, one which is manually operated to follow the trace of pressure on the flow chart placed on a rotating table, and the other is manually operated to follow the trace of differential pressure. An operator has two rotatable operating arms which are linked to the two pen arms, and by operating each of the operating arms by one hand, he simultaneously tracks both of the traces with the two pen arms.
For many years the mechanical integrators have used the angles of rotation of the two operating arms and the rotation of the table to provide a continuing product, which represents the instantaneous flow rate, and by integrating flow rate with time, or rotation of the chart, the flow during the selected time interval is provided.